--help should always go to stdout

The standard convention is that the  output of --help should go to standard
output (so that it can be piped to a pager and searched.) See, e.g., the
GNU coding standards.

https://bugzilla.gnome.org/show_bug.cgi?id=737194

src/ostree/ot-admin-builtin-instutil.c

@@ -119,12 +119,14 @@ ot_admin_builtin_instutil (int argc, char **argv, OstreeSysroot *sysroot, GCance
 
   if (subcommand_name == NULL)
     {
+      void (*print_func) (const gchar *format, ...) = want_help ? g_print : g_printerr;
+
       subcommand = admin_instutil_subcommands;
-      g_print ("usage: ostree admin instutil COMMAND [options]\n");
-      g_print ("Builtin commands:\n");
+      print_func ("usage: ostree admin instutil COMMAND [options]\n");
+      print_func ("Builtin commands:\n");
       while (subcommand->name)
         {
-          g_print ("  %s\n", subcommand->name);
+          print_func ("  %s\n", subcommand->name);
           subcommand++;
         }
 

src/ostree/ot-builtin-admin.c

@@ -147,12 +147,14 @@ ostree_builtin_admin (int argc, char **argv, OstreeRepo *repo, GCancellable *can
 
   if (subcommand_name == NULL)
     {
+      void (*print_func) (const gchar *format, ...) = want_help ? g_print : g_printerr;
+
       subcommand = admin_subcommands;
-      g_print ("usage: ostree admin --sysroot=PATH COMMAND [options]\n");
-      g_print ("Builtin commands:\n");
+      print_func ("usage: ostree admin --sysroot=PATH COMMAND [options]\n");
+      print_func ("Builtin commands:\n");
       while (subcommand->name)
         {
-          g_print ("  %s\n", subcommand->name);
+          print_func ("  %s\n", subcommand->name);
           subcommand++;
         }
 

src/ostree/ot-main.c

@@ -201,7 +201,7 @@ ostree_run (int    argc,
           g_set_error_literal (&error, G_IO_ERROR, G_IO_ERROR_FAILED,
                                "No command specified");
         }
-      ostree_usage (argv, commands, TRUE);
+      ostree_usage (argv, commands, !want_help);
       goto out;
     }